Pitch Memory : An Advantage for the Left - handed

In an auditory or musical memory task, subjects made pitch recognition judgments when the tones to be compared were separated by a sequence of interpolated tones. The left-handed subjects performed significantly better than the righthanded and also had a significantly higher variance. Further analysis showed that the superior performance was attributable largely to the left-handed subjects with mixed hand preference. 559 o n A ug us t 7 , 2 00 7 w w w .s ci en ce m ag .o rg D ow nl oa de d fr om to the subjects and they were-given four practice sequences (4). The subjects were 76 right-handed and 53 left-handed university undergraduates (5). The average error rates for these two groups are shown in Table 1. The variance of the left-handed group was significantly higher than that of the right-handed group [P < .05 (6)]. Further, the lefthanded subjects made significantly fewer errors than the right-handed (median test, x2 = 8.03, d.f. = 1, P < .01) (7). Given the larger variance in the lefthanded group, I hypothesized that those who were strongly left-handed might differ from those with a mixed preference, since individuals in the latter group would be expected to have more bilateral representation of function (8). Each population was therefore subdivided on the basis of strength of manual preference (Table 1) (9). There was an overall significant difference among these four subgroups (median test, x2 = 12.33, d.f. = 3, P < .01). Further, the performance of the left-handers with a mixed preference (moderately left-handed) was significantly more accurate than that of any of the other three groups (Table 1). The other groups did not differ significantly from each other. These findings suggest an explanation in terms of a duplication of storage of pitch information by the moderately lefthanded. If the efficiency of storage and retrieval at one locus is identical for all populations, then the retrieval of this information from two separate loci should significantly increase the overall probability of correct judgment. We can further hypothesize that such duplication of representation occurs in parallel with the duplication of representation of speech functions in the two hemispheres. We cannot, of course, specify whether the pitch information is retained in the dominant or the nondominant hemisphere in the case of people for whom a more completely unilateral storage is hypothesized (10). It remains to be determined to what extent the superiority of the moderately left-handed on this pitch memory task generalizes to other auditory or musical situations. However, other left-handed subjects selected for previous esxperiments on the basis of superior performance on such a task performed unusually well on a variety of tests of musical memory, including the transposition of melodic sequences (11). The finding that the moderately lefthanded differ significantly in performance from the moderately right-handed also demonstrates that the "ambidextiis't sh l not& c i a single population, as is often assuithed. Had the two groups been comibined in this study, no significant differences would have been seen (12).